Flexible packaging such as thermoplastic film is commonly used in form/fill/seal equipment for packaging fluid material such as food products. In form/fill/seal systems, material is placed inside tubular thermoplastic film and the top and bottom of the tubular film is heat sealed with a heat seal die to encase the material. Condiments such as ketchup and mustard are often packaged this way.
Temperature variation across the length of the heat seal die can produce packages that leak fluid material or serum over a period of time. This phenomenon occurs when the sealing temperature of the end seal dies exceeds or falls below the sealing range of the material. These suspect packages may not be evident to the operator of the form/fill/seal machines since the temperature controller only senses the temperature on one small area of the die. This condition often results in contamination of entire boxes of packaged goods containing large numbers of individual packets of product. Therefore, there is a need for more reliable form/fill/seal equipment.